Preheat your oven to 350 F (175 C). Grease a pie dish with cooking spray.
Mix the base: in a medium-sized bowl, mix the eggs, oil, Parmesan cheese, parsley, mustard powder, garlic powder, salt, and pepper until well combined.
Add the vegetables and Bisquick: Gently fold in the sliced zucchini, chopped onions, bell peppers, and Bisquick mix, mixing just until no dry bits of Bisquick remain; lumps are ok.
Bake: Pour the mixture into the greased pie dish. Bake for 30 minutes, or until the top is golden brown and a toothpick instead in the center comes out clean.
Cool and Serve: Allow the pie to cool for a few minutes before slicing. For added flavor, serve with extra Parmesan cheese on top.